Compensating hairspring



Patented Sept. 18, 1951 No Drawing. ppl cation June 1,1950, Serial No. 165,577. Switzerland June to, 1949 ;4 Claims. (01. 7542s The alloys oi. iron and nickel that havebeen investigated by numerous research workers, particularly by Guillaume, Hanson and, Hanson, Peschard, Honda and Miura, Merz, Kase, sch'eil,

Jette and Foote, Chevenard, are divided into two i The culminating point of this technique has been attained by the researches carried out bythe .Socit des tFabriques de Spiraux Runies with the Socit anonyme de Commentry Fourchamgroups, the irreversible ferro-nickels and the re versible ferro-nickels, according to thepercentage of nickel, the limit being between 27 and 28 per cent. For clearance of exposition. the limit indicated by Professor Chevenard, namely 27.3% of nickel',

u will be adopted.

It is moreover well known, since the scientific works of Dr. Guillaume, that the thermo-elastic anomaly that is characteristic of these alloys utilised in chronometry for making compcnsat ing hair-springs of the elinvar type is .to'be found between the limits of 27.5 and 44 per cent,

Made without addition, these alloys have a constant elastic force at 27.5 and 44 per cent,

whereas the thermo-elastic coeflicient is positive in the intervening range, exhibiting a maximum in the neighbourhood of 36 per cent. Beyond and below these limits the thermo-elastic coeiiicient becomes negative, and the hairspringscompensate only partially, and the more imperfectly as they move farther away from the limits indicated. V

Below 27.5% the thermo-elastic coeflicient is negative, without however reaching the value of that of steel. Hairsprings made of alloys in this category can therefore already eifeot a partial compensation, without however attaining'accurate compensation, which can only be realised above 27.5%. Without auxiliary additions these alloys are very soft, and for this reason practically unutilisable (see Swiss Patent No. 15527). I

The alloy at 27.5 is still very soft. In order-to harden it Dr. Guillaume incorporates therein additions of chromium, tungsten, molybdenum or other hardening agents.

These additions diminish the breadth'of the thermo-elastic anomaly. Compensating hairsprings rendered more elastic by this means require to have a nickel content of between 27.5 and 42%, and the proportioning is effected in such a way that the positive anomaly is diminished down to zero by the effect of the hardening additions, correcting or not correcting the secondary error (Swiss Patents Nos. 54,876, 89,576 and 82,081).

The hairsprings manufactured on the basis of Swiss Patents Nos. 160,798 and 196,408 utilise the same process, except for the difference that while still employing the hardening additions mentioned by Guillaume they include an additionoi beryllium.

bault Decaizeville, while thestructural hardening process has'been added to the hardening effect of the additions (Swiss Patents Nos. 217,548 and 217,814)

As is explicitly mentioned in Swiss Patents Nos. 21'7,548 and 217,814, all the alloys hitherto utilised, and mentioned in the present exposition,

, are reversible ferro-nickels, that is to say, austenitic solutions containin iron in the gamma state.

, V For an alloy having a grade higher. than 27.3%

of. nickehthe austenitic state is determined solely by the nickel content (zone of the reversible ferro -nickels) pliance which maintains fixed the extremity of For the alloys containing less. than 27.3% ,of nickel, and being in the irreversible zone, the gamma 'allotropic state of the iron is imposed by the temperature of fixing (the last manufacturing operation, in the course of which the hairsprings are passed through a furnace inorder to give them the final form), which is above 550 C. (see Swiss Patent No. 196.408). This temperature implies the passage into the gamma state of all the irreversible alloys containing more than 25% of nickel. By cooling down to the surrounding temperature, the return to the alpha state never takes place when the alloys contain the hardening additions mentioned in all the patents cited. with the sole exception of Swiss Patent No. 15,527.

This latter patent describes a hairspring the compensating power of which is insuflicient, as Dr. Guillaume has indicated in the patents taken out subsequently, and its characteristic as a soft alloy, expressly mentioned in the patent, is a determining feature as regards its austenitic structure.

In spite of all the hardening additions incorporated in large percentages, sometimes going as far as 30%, and far exceeding the percentages ordinarily employed in metallurgy, these austenitic solutions have never been able to attain the elastic limit of tempered hairsprings.

This elastic limit is measured, amongst hairspring-manufacturers, with the aid of a small apthe outer turn of a standard hairspring (size 72, utilised for 45-millimetre chronometers), while the extremity of a rod is embedded at the centreof the hairspring. The length of the penetration before deformation intervenes character- 3 ises the elastic limit, which is thus measured in millimetres.

Hairsprings realising excellent compensations support elongations of 75 to 100 millimetres, and in exceptional cases 110 to 115 millimetres, without appreciable deformation, while tempered steel hairsprings easily go as far as 150 millimetres.

On the other hand, on account of the high temperature at which they have to be fixed, which may be in the neighbourhood of 700'C., but are more generally above that, the hairsprings become tarnished by oxidation on passing through the fire, the turns stick together and-become very dlflicult to disengage, and the operation often proves impossible without deformation,owing to their low elastic limit. These deformations, which without having to wait a very long time, this render the hairsprings useless, constitute-in fact the principal difiicultyiof this industry. -'I he.present invention obviates all these disadvantages, not by incorporating infthe alloynew andbulky-additions, as has been the-practice hitherto, butbymodifying the basic structure in vsuch a way that inthe-finished hairspring'the iron is in the alpha allotropic state rather'than inthe gamma state.

'Whereas all the research-workers who-have o'c- -cupied themselves with this problem have belllieved that only gamma austenitic solutions permitted perfect compensation to be realised, the .author of thepresent-invention has discovered that such compensation can be perfectlyrealised by utilising a ferritic alloy containing iron in the alpha state, but that then the proportions of. nickel'utilised should no'longer vary between 27.5 and 43% but only within the narrowlimits of 24.5 to 27%, 27.3% being the Ilimitat which thealloy becomes reversible and "a'ustenitic, "as "mentioned above. When the compensatin elementis thus constituted 'withinthese limitsby "the 'alpha-iron-nickel complex "rather "than by the gamma-ir'on nicke1 complex, "the hairsprings reveal "an elastic limit which 'n'ow not cnly'rigor- -'ous1 attainsthe elastic iimit'oftempere'd 'hairsprln'gs but even surpa'sses it in a'pr'op'ortion 0f to since the standard test "onhairspririgs *size '72 permits elongatio'ns 'without'd'eform'ati'on going "as -far as 170 millimetres instead of 150 'millimetres for tempered hairsprings and 75 to "100 millimetres for the usual-compensating :hairsprings.

The 'ma'intenance of the-structure of 'the -iron in-the alpha state requires a fixing'temperature below the alpha-gammatransformation'poinbof "the irreversible alloyscontaining from-24*to-'27% 'of nickel, 'that is tosay, below 550 C. impractice it-shouldnot=exceed'500-C. This=low temperature=eliminates all the manufacturing troubles mentioned above, such as stains, and turns adhering to one another in fixing, with subse- -vention shows that columbium incorporated in the alloy withacontent ofrfrom 1 to 5% enables .the desiredresult to be attained.

A slight addition of carbon of -from. 0.20 to 0.70% likewise. facilitates .the operation.

In certain cases the carbon may be omitted, and the columbium replaced partially by an addition of aluminium, but in a percentage always lower than A; of the columbium addition. Furthermore, an addition of manganese of from 0.5 to 1% remains necessary because it facilitates forging without exerting any other special in- :fiuence.

Besides the defects already mentioned, austenitic compensating hairsprings are often unstable;

instability may reveal itself by an instantaneous g'oing't'est, such as can be carried out with the modern quartz-oscillator machines. The test consists in verifying the going of the watch at the moment when theregulating has just been com- *pleted, and'repeating it one hour later. The ,variation in going is a characteristic indication of the instabilit of the hairspring.

While austenitic hairsprings reveal variations which in the'best results are from 11 to 12 seconds, in which in'certain cases reach to seconds or more, the hairsprings of alpha-iron structure forming the subject of the presentinvention have disclosed variations of going lower than 3 seconds, and often even no change at all has been ascertainable. Such a result had never hitherto been attained, even with tempered hairsprings.

'30 An'alloy comprising the following percentages:

'Per'cent Nickel 24 to'27 Carbon 0:20to "0.7 Columblum 1 to 5 Manganese "0.5 "to-'1 Iran, the "remainder.

renders it possible to manufacture strictly compensating -hairsprings of ,anflelasticity not merely equal to butevengreater than that-of tempered .hairsprings, and-such that tests of variation 0f runningmarried out -just after the termination of the regulating give promise of extraordinary stability.

This alloy further eliminates enormous vdiili- '-culties--in manufacture, on account of the-fixing temperature being lower than 550 C.

In the annealed state, this irreversible-alloy (is austenitic. The alpha allotropic'state-ofiron, which is characteristic of the present invention, is obtained slowly by intense drawingin a cold state atthe time of manufacturing the wire, and then at the time of rolling the latterinto astrip constituting the turns of the-hairsprings. Any fixingabove 550 destroys both thestructureand the adjustmentof thecorrect-compensating prop- :erties.

By way of indication, a ha-irspring made with this alloy may reveal a thermal coefiicient =not exceeding 0.05 of a second, if it iseoupled to-an ordinary balance-wheel of :the uncut-nickel type, whereas-if the'fixing is eflected at atemperature of600 the samealloy will pass to-the austenitic state, it willimmediately become very-soft, the advantages of stability -will likewise disappear, -and the-compensating power 'will'be greatly reduced, the thermal coeificient becoming modified asfar as 7" per degree, whilea coefiicient-of 11 to :12 seconds corresponds to the complete ab- -.sence of compensation when the -same balancewheel is coupled to a steel hairspring.

What Iclaim is:

1. A compensating hairspring of an elasticity at least equal to that of tempered steel ,hairsprings, and constituted by an alloy such thatthe strict compensation obtained by association with a mono-metallic balance-wheel of the uncut nickel type is ensured by the aid of the alpha-ironnickel complex, the nickel being in a proportion of 24 to 27 per cent., with auxiliary additions composed in such a way that the temperature permitting perfect fixing to be obtained is at the maximum 550 degrees centigrade, constituted by an alloy the composition of which is included between the following limits:

Per cent Nickel 24 to 27 Carbon 0.20 to 0.7 Columbium 1 to 5 Manganese 0.5 to 1 Iron, the remainder.

2. A compensating hairspring of an elasticity at least equal to that of tempered steel hairsprings, and constituted by an alloy such that the strict compensation obtained by association with a monometallic balance-wheel of the uncut nickel type is ensured by the aid of the alphairon-nickel complex, the nickel being in a proportion of 24 to 27 per cent., with auxiliary ad- .ditions composed in such a way that the temperature permitting perfect fixing to be obtained is at the maximum 550 degrees centigrade, constituted by an alloy the composition of which is included between the following limits:

Per cent Nickel 24 to27 Columbium 1 to 5 Manganese 0.5 to 1 Iron, the remainder;

tuted by an alloy the composition of which is included between the following limits:

Per cent Nickel 24 to 2'7 Carbon 0.20 to 0.7 Manganese 0.5 to 1 Columbium and aluminium together, the proportion of aluminium not exceeding of the quantity of columbium 0.1 to 5 Iron, the remainder.

4. A compensating hairspring of an elasticity at least equal to that of tempered steel hairsprings, and constituted by an alloy such that the strict compensation obtained by association with a monometallic balance-wheel of the uncut nickel type is ensured by the aid of the alphairon-nickel complex, the nickel being in a proportion of 24 to 27 per cent., with auxiliary additions composed in such a way that the temperature permitting perfect fixing to be obtained is at the maximum 550 degrees centigrade, constituted by an alloy the composition of which is included between the following limits:

Iron, the remainder.

ERNEST DUBOIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,507,698 Dubois May 16, 1950 FOREIGN PATENTS Number Country Date 15,527 Switzerland Apr. 21, 1898 

1. A COMPENSATING HAIRSPRING OF AN ELASTICITY AT LEAST EQUAL TO THAT OF TEMPERED STEEL HAIRSPRINGS, AND CONSTITUTED BY AN ALLOY SUCH THAT THE STRICT COMPENSATION OBTAINED BY ASSOCIATION WITH A MONO-METALLIC BALANCE-WHEEL OF THE UNCUT NICKEL TYPE IS ENSURED BY THE AID OF THE ALPHA-IRONNICKEL COMPLEX, THE NICKEL BEING IN A PROPORTION OF 24 TO 27 PER CENT., WITH AUXILIARY ADDITIONS COMPOSED IN SUCH A WAY THAT THE TEMPERATURE PERMITTING PERFECT FIXING TO BE OBTAINED IS AT THE MAXIMUM 550 DEGREES CENTIGRADE, CONSTITUTED BY AN ALLOY THE COMPOSITION OF WHICH IS INCLUDED BETWEEN THE FOLLOWING LIMITS: 